Slightly fancier is instead to select the images, and choose the create option where you can use a bunch of Apple templates, but instead of paying Apple to print the book at the end just print it as a PDF, then print it yourself. This is probably better for a year end year book than posters, but I'm sure you can make it work for either if you really want to...

If you really insist on something prettier, resize them in Preview, then drag and drop them all into Keynote, they will all be placed on separate slides, choose a theme you like, and then add the text yourself.